The invention relates generally to packet-based communications networks and, more particularly, to a system for controlling the routing of packets in a packet-based communications network that is especially apt for use in a satellite communications network.
Satellite communications systems generally include a plurality of communications satellites that orbit a primary body (such as the earth) on substantially fixed paths. The plurality of communications satellites (known as a satellite constellation) forms a communications network having a node at each satellite location. Each satellite in the constellation generally has the ability to communicate with one or more ground stations on the earth""s surface (via uplinks and downlinks) as well as with other satellites in the constellation (via crosslinks). Using these satellite capabilities, the satellite communications system can establish a channel of communication between users in geographically diverse places on earth. Global satellite communications systems are currently in development that will be capable of providing continuous communications coverage to most areas of the earth""s surface.
To deliver information via a satellite communications system, the following procedure is generally followed. First, information is delivered from a first user to a satellite ground station via, for example, local telephone lines. The local ground station packetizes the information and transfers the information packets to a source satellite in the constellation via an established uplink to the satellite. The information packets are then transferred through the satellite network, via crosslinks, until a destination satellite is reached. The destination satellite then transmits the information packets, via an established downlink, to a second ground station that is proximate to the second user. The second ground station recombines the information packets and delivers the information to a second user via local telephone lines.
In general, a satellite communications system will be highly meshed, i.e., there will be many different routes between two nodes (i.e., satellites) in the network. Therefore, an important at consideration in a satellite communications system is the selection of a route through the network from the source satellite to the destination satellite. For example, it is desirable that a route through the network be chosen that minimizes traffic congestion in the network. Prior satellite routing systems generally perform a time consuming investigation of each of the available routes during a call setup period before assigning a route to a given connection. In addition to being relatively slow, these prior systems require a great amount of processing overhead during call setup. Further, due to limitations in the ability of such systems to account for network usage, the prior systems are not generally capable of performing optimal network resource management. That is, because the system must perform investigations prior to route assignment, and is not privy to a prior knowledge of network resource usage, optimal management of resources is generally unattainable. Also, in satellite systems using polar orbits, prior routing systems do not provide the degree of flexibility necessary to handle the satellite xe2x80x9chand-offsxe2x80x9d that are periodically performed,
Therefore, a need exists for a method of routing packets in a satellite communications system which is capable of rapidly choosing an optimal route through a satellite communications network during a call setup period. In addition, a need exists for a method of routing packets that requires relatively little processing to achieve a substantially optimal route. Further, a need exists for a method of efficiently, flexibly and optimally managing network resources in a satellite communications system.